The present invention relates to a measurement cell for analyzer for qualitative and/or quantitative analysis for substances contained in blood, urine, water or the like, and an analyzer using the cell.
In an analyzer for qualitative and/or quantitative analysis for a small amount of elements contained in blood, urine, water (e.g., drinking water and river water) or the like, a liquid sample is usually placed in a rectangular parallelepipedic cell and subjected to qualitative and/or quantitative analysis by measuring an optical property such as absorbance, transmittance, reflectance, fluorescence intensity or the like. Even when one sample is analyzed, the measurement of two or more items requires samples for measurement in the same number as that of the items. For example, in the case of urine, sugars, proteins, pH, ketone bodies, blood, urobilinogen, bilirubin, amylase and the like are measured. In the case of blood, cholesterol, cholinesterase, phosphatase, GOT, GPT and the like are measured. In the case of water, pH, contained elements (e.g., ions of metals such as sodium, cadmium, lead etc., chlorine ions and cyano ions), turbidity and the like are measured. Although there are very few methods each for carrying out qualitative and/or quantitative analysis for two or more substances among the above-exemplified substances, one analysis method is adopted for qualitative and/or quantitative analysis for each substance in most cases. Therefore, cells in the same number as that of measurement items are necessary even when one sample is analyzed. For example, in the case of blood, there are about 60 measurement items.
In the case of a blood analyzer, the miniaturization of a cell is in progress in order to reduce the amount of a sample for analysis as much as possible for the purpose of reducing a burden on a human being who takes an examination. However, when the cell is miniaturized, the sample becomes difficult to place in the cell. Even if the sample can be placed in the cell, bubbles remain in the cell, so that exact measurement by absorbance, transmittance and the like cannot be made. This problem is remarkable when the surface tension of the sample is high. In addition, the cell once used is washed and a liquid used for the washing is removed from the cell by suction or drying, after which the cell is reused for the measurement. Therefore, the cell requires a washing step. Since the cell is often a rectangular parallelepiped, the position of a nozzle for water jet is required to be accurate for certain introduction of water for washing into the cell in order to wash the interior of the cell. Moreover, for the same reason as above, the exhaust of a liquid sample and the injection and exhaust of a washing liquid become difficult also in the washing of the cell with a decrease of the size of the cell. That is, also in this regard, the miniaturization of the cell is limited. The bubbles can be removed in some cases by vibrating the cell with an ultrasonic washer or the like, but the cell should be vibrated also in washing of the cell in order to fill the cell with water for washing. Therefore, a large-scaled apparatus is necessary.
As a method for reducing the amount of a sample which is required for the measurement, there is also a method of increasing the volume of the sample by diluting the sample with water. However, if the sample is diluted with water, the resulting sample has a high surface tension and hence is more difficult to place in a small cell, as described above. In addition, the ratio of the absorbance of the sample to that of a reference is decreased by the dilution, resulting in a low precision of measurement. For the dilution, an alcoholic organic solvent is used in some cases in place of water but is disadvantageous in that there are samples hardly soluble in solvents other than water or that the absorption spectrum of the resulting dilution is changed by the addition of an indicator. As described above, the reduction of the amount of a sample is difficult in a measuring method using a present-day rectangular parallelepipedic cell.
As a prior art, there is xe2x80x9cTest Piece for Liquid Sample and Process for Production Thereofxe2x80x9d (JP-A-11-14617). This test piece has a structure in which sample-holding portions comprising a water-soluble polymer and an indicator are provided on the surface of a polystyrene plate, and it permits measurement using a sample in an amount smaller than that required in the case of a rectangular parallelepipedic cell. The test piece, however, cannot be reused after washing unlike an ordinary measurement cell because the indicator has been previously held in the sample-holding portion. The reason is that the test piece invented is similar to pH test paper and the like.
As described above, when items measured for even one sample are increased, the number of cells used is increased, so that a necessary number of cells should be prepared. Moreover, cells in a number necessary for the measurement items should be washed after the measurement.
The amount of a sample cannot be reduced merely by miniaturizing a measurement cell having a conventional structure or by diluting the sample.
There has been a desire for a cell and a measuring apparatus which makes it possible to measure two or more items for one sample and make the amount of the sample smaller than that required at present. The cell should be repeatedly used by operations such as washing.
We investigated in order to solve the above problems, and consequently found that the following flat plate functions as a cell capable of solving the above problems (hereinafter referred to as xe2x80x9cflat cellxe2x80x9d); a flat plate which is made of a material capable of transmitting or reflecting measuring light and has a water-repellent surface formed thereon and having a plurality of hydrophilic patterns. On the basis of this finding, the present invention has been accomplished.
The details of means for solving the above problems are described below.
(1) A measurement cell for analyzer for carrying out qualitative and/or quantitative analysis for one or more substances by an optical means, which has the following characteristics: a sample to be subjected to measurement is liquid; the shape of said measurement cell is substantially planar; the cell has sample-holding portions in said plane; the contact angle between the sample-holding portion and water is 30xc2x0 or less; the contact angle between the other portion of said plane and water is 100xc2x0 or more; and said measurement cell can be repeatedly used by washing and drying.
(2) The measurement cell for analyzer according to the above item (1), characterized in that a layer of a compound having any of the following structures is formed on the portion other than the sample-holding portions:
[F{CF(CF3)xe2x80x94CF2O}nxe2x80x94CF(CF3)]xe2x80x94Xxe2x80x94Si(OR)3 
{F(CF2CF2CF2O)n}xe2x80x94Xxe2x80x94Si(OR)3 
{H(CF2)n}xe2x80x94Yxe2x80x94Si(OR)3 
{F(CF2)n}xe2x80x94Yxe2x80x94Si(OR)3 
wherein X is a linking site between a perfluoro polyether chain and an alkoxysilane residue, Y is a linking site between a perfluoroalkyl chain and an alkoxysilane residue, and R is an alkyl group.
(3) An analyzer for qualitative and/or quantitative analysis for one or more substances by an optical means, which has the following characteristics: a sample to be subjected to measurement is liquid; the shape of cells used for the measurement is substantially planar; each of the cells has sample-holding portions in said plane; the contact angle between the sample-holding portion and water is 30xc2x0 or less; the contact angle between the other portion of said plane and water is 100xc2x0 or more; said measurement cells can be repeatedly used by washing and drying; and the analyzer has therein at least a conveying mechanism for said cells, a sample sticking mechanism, an indicator sticking mechanism and an optical measurement mechanism.
(4) The analyzer according to the above item (3), characterized in that a layer of a compound having any of the following structures is formed on the portion of said cell which is other than the sample-holding portions:
[F{CF(CF3)xe2x80x94CF2O}nxe2x80x94CF(CF3)]xe2x80x94Xxe2x80x94Si(OR)3 
{F(CF2CF2CF2O)n}xe2x80x94Xxe2x80x94Si(OR)3 
{H(CF2)n}xe2x80x94Yxe2x80x94Si(OR)3 
{F(CF2)n}xe2x80x94Yxe2x80x94Si(OR)3 
wherein X is a linking site between a perfluoro polyether chain and an alkoxysilane residue, Y is a linking site between a perfluoroalkyl chain and an alkoxysilane residue, and R is an alkyl group.
(5) A cell for subjecting a sample to measurement which has two or more hydrophilic patterns having a contact angle with water of 30xc2x0 or less and a water-repellent portion having a contact angle with water of 100xc2x0 or more, and is planar.
(6) The cell according to the above item (5), which transmits 60% or more of light having a wavelength of 340 to 800 nm which is incident upon the cell.
(7) The cell according to the above item (5), which transmits 80% or more of light having a wavelength of 400 to 800 nm which is incident upon the cell.
(8) The cell according to the above item (5), wherein a plate for the cell is a metal that reflects light.
(9) The cell according to the above item (5), wherein the surface roughness of the sample sticking area is Ra 100 nm or less.